The invention relates to a light-scattering layer on a transparent body, in particular consisting of a glass or a glass ceramic, as well to a method producing such a layer. More particularly, the invention relates to a method of preparing a light-scattering layer on a glass ceramic cooktop.
It is known to apply organic colors onto glass ceramic cooktops by printing the colors onto a nap pattern on the lower side of the glass ceramic cooktop. This coating shall avoid a lateral emerging of light, in particular when halogen irradiation heaters are utilized. To this end, usually a black paint is utilized which is temperature-resistant only to a maximum of 250° C. (permanent resistance) or to about 350° C. (short-time resistance), respectively. Therefore, in any event it is necessary to spare the hot region above the heating elements from the
Ceramic colors, such as commonly utilized for the decoration of the top surfaces of glass ceramic cooktops cannot be used on the lower side of a glass ceramic cooktop, since they reduce the mechanical stability during baking such that a sufficient impact resistance is not provided any more. Herein the impact resistance deteriorates to values below 0.5 Joule.
From U.S. Pat. No. 6,037,572 it is basically known to apply ceramic particles by thermal spraying onto a surface of a glass ceramic.
However, the glass ceramic layer produced in this way is only intended as an insulation layer in glass ceramic cooktops that are provided with a contact heater on the lower side of the glass ceramic plate. Such an insulation layer is necessary when using contact heaters, since the electric resistance of a glass ceramic decreases with increasing temperature (NTC characteristic). An insulation layer manufactured in this way thus comprises a large layer thickness on the order of several hundred micrometers and is optimized with respect to its insulating characteristics. In addition, there is an adhesion problem when applying ceramic particles by thermal spraying onto a glass or a glass ceramic surface. Namely, it has been found that the common pretreatment of the surface to be coated by surface roughening blasting is not possible, since thereby the mechanical stability of the glass or glass ceramic surface is impaired.